Piston Pump With Improved Pressure Build-Up Dynamics

ABSTRACT

A piston pump for delivering hydraulic fluid, having a piston that is able to move in a reciprocating fashion in order to build up pressure in a pressure chamber and having at least one valve equipped with a spring sealing element having a sealing region and a spring region in order to open and close an opening.

PRIOR ART

The present invention relates to a piston pump for delivering hydraulic fluid with improved pressure build-up dynamics.

A wide variety of piston pump designs are known from the prior art. Piston pumps for vehicle brake systems are frequently embodied in the form of radial piston pumps, in which at least one piston can be set into a reciprocating motion by means of a cam. Piston pumps of this kind are frequently used in connection with electronic stability systems (ESP) or electrohydraulic brake systems (EHB). Basically, the known piston pumps have a pressure chamber situated between an inlet valve and an outlet valve and the movement of the piston builds up a pressure in this pressure chamber. In order to achieve the most compact design possible, there are known piston pumps in which the hydraulic fluid is supplied to the pressure chamber by means of bores provided in the piston. The inlet valve is situated at the pressure chamber end of the piston in the pressure chamber. In this connection, a cage-like retainer must be provided in the pressure chamber for a return spring of the inlet valve. The pressure chamber also contains a return spring for the piston. This large number of parts in the pressure chamber requires a relatively large amount of clearance in such piston pumps. In addition, piston pumps of this kind have only limited pressure build-up dynamics. In the known piston pumps, outlet valves are also used, which are comprised of a sealing seat, a valve-closing ball, a spring for the ball, and a retaining element for the spring. Consequently, the valves of the known piston pumps have a relatively large number of parts, which entails a certain assembly expenditure. Moreover, the known piston pumps have a certain length in the axial direction.

ADVANTAGES OF THE INVENTION

The piston pump according to the invention, which is for delivering hydraulic fluid and has the characterizing features of claim 1, has the advantage over the prior art of having a small number of parts. This permits a significant reduction in the manufacturing and assembly costs. Due to the reduced number of parts, the piston pump according to the invention is also compact, particularly in the axial direction of the piston pump. This is achieved according to the invention by virtue of the fact that at least one valve of the piston pump has a spring sealing element. The spring sealing element is composed of a spring region and a sealing region. In other words, according to the invention, a one-piece spring sealing element is provided, which performs both the function of a valve-closure element and the function of a valve spring. Consequently, the number of parts in a pressure chamber of the piston pump is reduced so that the structural size is minimized.

The dependent claims disclose advantageous modifications of the invention.

Preferably, the spring sealing element is embodied in the form of a plate-shaped element and includes a sealing region, a spring region, and a retaining region. As a result, the piston pump according to the invention can be particularly compact and small since the valve requires only the amount of space occupied by the thickness of the plate-shaped element. In addition, a retaining region is also integrated into the spring element.

It is particularly preferable for the spring region of the spring sealing element to be embodied so that it has at least one spring coil.

It is also preferable for the retaining region of the spring sealing element to be embodied in an annular form. On the one hand, this permits a rapid and simple fixing of the spring sealing element and on the other hand, the annular retaining region lends the spring sealing element a certain amount of stability.

In order to obtain an improved sealing action, the spring sealing element preferably seals against a through opening in a valve plate. In this case, the valve plate performs the function of a valve seat. It is particularly preferable for the valve plate to be manufactured of a plastic, in particular PEEK. It is also preferable for the plastic to be reinforced by means of carbon fibers.

Preferably, the valve is situated together with the spring sealing element inside a cylinder element in which the piston moves.

The piston pump valve according to the invention can be provided as an inlet valve and/or outlet valve of the piston pump. It is particularly preferable, however, for the valve to be provided as an inlet valve and for the spring sealing element to be situated in the pressure chamber of the piston pump. The integral design of the spring sealing element makes it possible to minimize the clearance in the piston pump. In addition, it is possible for an inlet bore of the piston pump to have a very large diameter so as to achieve the lowest possible flow resistance through the inlet bore during the intake phase. This makes it possible to further improve the efficiency of the pump.

The plate-shaped spring sealing element is thus a kind of leaf spring placed over a through opening of the valve and has a disk-shaped sealing region that has a diameter slightly larger than the diameter of the through opening. A seal is thus produced at the edge of the disk-shaped sealing region.

It is also preferable if a return spring for a piston is situated in the pressure chamber of the piston pump in such a way that the return spring is supported against the retaining region of the spring sealing element. This permits an additional fixing of the spring sealing element.

It is particularly preferable if the valve is embodied in the form of an inlet valve of the piston pump and is situated in a cylinder element of the piston pump in such a way that a through flow direction of the inlet valve is the same as a movement direction of the piston during the intake phase of the piston pump. This achieves a particularly flow-favorable path during the intake phase of the piston pump. This can improve the efficiency of the piston pump.

In addition, it is possible to achieve a piston pump with a very small structural size in the radial direction of the piston. This is achieved by virtue of the fact that a spring element of a valve of the piston pump is preferably embodied in the form of a spring ring. Embodying the spring element in the form of a spring ring means that in addition to its spring function, the spring element can also be situated in the piston pump in such a way that no additional components are required for fixing the spring ring since the annular form of the spring ring allows it to be affixed to an existing component of the piston pump without requiring additional parts.

The spring ring preferably has a slit. It is possible to adjust the spring force of the spring ring by embodying this slit in different ways. Consequently, one spring ring can be used for various applications and its spring force can be changed by varying the embodiment of the slit in the spring ring. It is preferable for the slit in the spring ring to be embodied as Z-shaped. The slit preferably passes through the width of the spring ring so that the spring ring is split in the circumference direction. It is also possible, however, to provide a number of slits in the spring ring, which do not divide the spring ring all the way across its width.

Preferably, the spring ring is placed in a groove provided in a cylinder element of the piston pump. This makes it possible to implement a particularly compact design.

In order to affix a valve-closure element to the spring ring, the inside of the spring ring is preferably provided with a recess. If the valve-closure element is a ball, then the recess is preferably a U-shaped channel or a partially spherical recess. This permits an automatic centering of the ball.

It is particularly preferable for the valve including the spring ring to be an outlet valve of the piston pump.

Preferably, a through opening, which can be opened or closed by the outlet valve, is situated in a cylinder element of the piston pump in such a way that a movement direction of the piston is perpendicular to an outflow direction through the through opening.

It is particularly preferable for the piston pump according to the invention to be used in vehicle brake systems, for example to control and regulate a pressure in a wheel brake cylinder. Preferably, the piston pump according to the invention is used in connection with electronic control and regulating systems of the brake system, e.g. ESP, EHB, TCS, etc. On the one hand, this can achieve cost advantages for such brake systems since the piston pump according to the invention is particularly inexpensive to manufacture and on the other hand, an efficiency of pump pistons and improved pressure build-up dynamics can be achieved, thus permitting a reduction in the reaction times of such brake systems.

DRAWINGS

The invention will be described in detail below in a preferred exemplary embodiment in conjunction with the drawings.

Drawings

FIG. 1 is a schematic side view of a piston pump according to an exemplary embodiment of the present invention,

FIG. 2 is a schematic, sectional, perspective view of the piston pump shown in FIG. 1,

FIG. 3 is a perspective, exploded view of individual parts of the piston pump shown in FIGS. 1 and 2,

FIG. 4 is a schematic top view of a spring sealing element according to the exemplary embodiment of the invention, and

FIG. 5 is a schematic top view of a spring ring according to the exemplary embodiment of the invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

A piston pump 1 according to a preferred exemplary embodiment of the invention will be described below with reference to FIGS. 1 through 5.

As is clear from FIG. 1, the piston pump 1 according to the preferred exemplary embodiment of the invention has a cylinder element 2 with a cylinder bore 2 a. The cylinder bore 2 a contains a piston 3, which is depicted in the detail shown in FIG. 3. The piston 3 includes a piston extension 3 a and two annular grooves 3 b and 3 c, and is moved by means of a cam that is not shown.

The cylinder bore 2 a contains a pressure chamber 7, which is hydraulically situated between an inlet valve 4 and an outlet valve 9. The inlet valve 4 essentially includes a spring sealing element 5, which is shown in the detail in FIG. 4. As is clear from FIG. 1, the spring sealing element 5 is plate-shaped and includes a disk-shaped sealing region 5 a, a spring region 5 b, and a retaining region 5 c. The spring region 5 b is embodied in the form of a spring coil and connects the sealing region 5 a to the retaining region 5 c. The spring sealing element 5 is placed against a valve plate 6 and seals against a sealing seat 6 b of the valve plate 6. The sealing seat 6 b here is situated along the circumference of the through bore 6 a in the valve plate 6. Consequently, the spring sealing element 5 seals against the sealing seat 6 b with an annular outer circumference region of the sealing region 5 a.

Hydraulic fluid flows to the inlet valve 4 via a supply line 8 and a connecting bore 17, which has the same diameter as the through bore 6 a of the valve plate 6 (see FIG. 1). The valve plate 6 is manufactured of a plastic material, in particular PEEK.

As shown in FIG. 1, the outlet valve 9 includes a spring ring 10 and a ball 11. The ball 11 seals against a sealing seat 12, which is provided in the cylinder element 2. The outlet valve 9 is situated at an outlet bore 18 and seals the pressure chamber 7 of the piston pump in relation to a pressure line that is not shown. The pressure chamber 7 also contains a return spring 13 in order to return the piston 3 to its starting position after it reaches its top dead center. As shown in FIG. 1, the return spring 13 rests against the retaining region 5 c of the spring sealing element 5. This provides an additional fixing of the spring sealing element 5 in the cylinder bore 2 a. It should be noted that the spring sealing element 5 can be installed in the cylinder bore 2 a by exerting a slight amount of pressure on it so that the spring sealing element 5 is also very easy to install.

The piston extension 3 a of the piston 3 achieves a clearance in the pressure chamber 7 that is as small as possible. The piston extension 3 also serves to guide the return spring 13. The piston also supports of sealing ring 14, a first guide ring 15, and second guide ring 16. As is clear from FIGS. 1 and 3, the sealing ring 14 and the first guide ring 15 are situated in the groove 3 b provided in the piston 3 and second guide ring 16 is situated in the groove 3 c provided in the piston 3. The sealing ring 14 seals the pressure chamber 7 of the piston pump in relation to a cam chamber. The guidance of the piston 3 in the cylinder bore 2 a by means of the first and second guide rings 15 and 16 is able to achieve a very rigid guidance of the piston.

The two guide rings 15 and 16 are spaced a relatively large distance apart from each other so that there is practically no possibility of the piston moving in a tilting fashion. The guidance of the piston 3 is thus in particular very insensitive to lateral forces on the piston 3, which can be transmitted from the cam drive to the piston.

As is also clear from FIG. 1, the inner circumference of the spring ring 10 is provided with a recess 10 a in order to partially accommodate the ball 11. The recess 10 a here is U-shaped in cross section. As is also clear from FIG. 1, the spring ring 10 is placed in a groove 2 b, which is provided on an outer circumference of the cylinder element 2. The spring ring 10 is embodied in the form of a closed ring and has a slit 19 in order to provide a certain amount of elasticity for the opening process of the outlet valve. The slit 19 is preferably Z-shaped and is preferably situated on the spring ring 10 opposite from the position of the ball 11 (see FIG. 5). It should be noted that the shape of the slit can be freely selected and that this shape exerts particular influence on the opening force of the spring ring 10. The slit of the spring ring 10 can, on the one hand, extend only partway into the spring ring 10 or can completely split the spring ring 10, so that the spring ring can be spread apart at the slit. It is also possible to provide a number of slits on the spring ring that do not completely split the spring ring 10.

The piston pump 1 according to the invention functions as follows. During an intake phase of the piston pump, the piston 3 moves toward the right in FIG. 1. As a result, the spring sealing element 5 opens due to the fact that the sealing region 5 a lifts away from its sealing seat 6 b on the valve plate 6. As a result, hydraulic fluid flows from the supply line 8 into the pressure chamber 7 via the connecting bore 17 and the through bore 6 a. During the intake phase, the outlet valve 9 is closed since a pressure prevailing in a pressure line, not shown, downstream of the outlet valve 9 acts on the spring ring 10 and thus holds the ball 11 against the sealing seat 12. Fundamentally, it should be noted that the outlet valve opening pressure is defined by the design of the spring ring. After the piston 3 has reached its bottom dead center and the direction of the piston 3 reverses, the compression phase of the piston pump 1 begins. This state is shown in FIG. 1. During the compression phase, the piston 3 moves in the direction of the arrow A in FIG. 1 so that pressure builds up in the pressure chamber 7. As a result, the inlet valve 4 closes because the pressure from the pressure chamber 7 acts on the disk-shaped sealing region 5 a. Since the disk-shaped sealing region 5 a has a relatively large area, this assures a rapid closing of the inlet valve. The farther the piston 3 moves toward its top dead center, the greater the pressure becomes in the pressure chamber 7. When the pressure in the pressure chamber 7 is greater than in a pressure line downstream of the outlet valve 9, the outlet valve 9 opens in that the spring ring 10, due to its elastic properties, is pushed radially outward by the ball 11 so that a connection opens between the pressure chamber 7 and the pressure line via the outlet bore 18 and the open outlet valve. Basically, it should be noted that the outlet valve opening pressure is defined by the design of the spring ring. This state is reached just before the piston reaches its top dead center. Pressurized fluid thus flows out of the pressure chamber 7, through the open outlet valve 9, and into the pressure line. After the piston 3 has reached the top dead center, its movement direction reverses once again and the intake phase begins anew; the outlet valve 9 is closed again by the spring force of the spring ring 10 and the pressure in the pressure line acting on the spring ring. The return spring 13 returns the piston 3 to its starting position, whereupon the intake phase begins once again.

As is clear from FIG. 1, the piston pump 1 according to the invention can have a very compact design since the inlet valve 4 is comprised practically exclusively of the one-piece spring sealing element 5. This permits a particularly compact design in the axial direction X-X of the piston 3. Although the inlet valve 4 is situated in the pressure chamber 7 of the piston pump 1, its presence does not require additional clearance. Moreover, the design of the inlet valve 4 according to the invention makes it possible to retain a large inlet bore (connecting bore 17 and through bore 6 a) so that a very high fill level of the pressure chamber is achieved with a minimal clearance, thus also achieving very favorable pressure build-up dynamics. In addition, an influx direction of the hydraulic fluid through the inlet valve 4 is the same as a movement direction of the piston 3 during the intake phase. This can achieve a further reduction in the losses during the influx of the fluid into the pressure chamber 7.

The outlet valve 9 is likewise comprised of a very small number of inexpensive parts and includes only the ball 11 and the spring ring 10. The spring ring 10 is preferably also manufactured of plastic and the assembly of the outlet valve 9 is very simple and inexpensive. The recess 10 a on the inner circumference of the spring ring also facilitates a correctly positioned installation of the spring ring.

The recess 10 a on the inside of the spring ring 10 to accommodate the ball 11 also has the function of preventing the spring ring 10 from rotating in relation to the cylinder element 2. In addition to being defined by the type of slit, the spring force of the spring ring 10 is also defined by its own thickness, width, and material composition.

The piston pump according to the invention consequently has a reduced number of parts, resulting in a very simple assembly, in particular of the inlet valve 4 and outlet valve 9, and in very low manufacturing costs. A very compact design of the piston pump can be achieved through the design of the plate-shaped spring sealing element 5 for the inlet valve and the design of the spring ring 10 for the outlet valve.

During the compression phase of the piston pump 1, the rising pressure in the pressure chamber 7 also achieves an improved seal at the inlet valve 4 since the pressure acts directly on the sealing region 5 a and the sealing region 5 a has a relatively large area. 

1-18. (canceled)
 19. A piston pump for delivering hydraulic fluid, the pump comprising a cylinder, a piston that is able to move in a reciprocating fashion in the cylinder in order to build up pressure in a pressure chamber, and at least one valve equipped with a spring sealing element having a sealing region and a spring region in order to open and close an opening.
 20. The piston pump according to claim 19, wherein the spring sealing element is embodied in the form of a plate-shaped element compressing the sealing region, the spring region, and a retaining region.
 21. The piston pump according to claim 19, wherein the spring region of the spring sealing element includes at least one spring coil.
 22. The piston pump according to claim 20, wherein the retaining region of the spring sealing element is embodied in an annular form.
 23. The piston pump according to claim 21, wherein the retaining region of the spring sealing element is embodied in an annular form.
 24. The piston pump according to claim 19, wherein the spring sealing element produces a seal against a sealing seat of a valve plate.
 25. The piston pump according to claim 19, wherein the valve is situated in the cylinder of the piston pump.
 26. The piston pump according to claim 19, wherein the valve is embodied in the form of an inlet valve of the piston pump and adjoins a pressure chamber.
 27. The piston pump according to claim 20, wherein the valve is embodied in the form of an inlet valve of the piston pump and adjoins a pressure chamber.
 28. The piston pump according to claim 27, further comprising a return spring for the piston, the return spring being is contained in the pressure chamber and resting against the retaining region of the spring sealing element.
 29. The piston pump according to claim 26, further comprising an outlet valve, the inlet valve and the outlet valve of the piston pump each having a spring sealing element.
 30. The piston pump according to claim 19, wherein the valve is embodied in the form of an inlet valve of the piston pump and is situated in the cylinder element in such a way that an influx direction of hydraulic fluid through an inlet opening is the same as a movement direction of the piston during an intake phase of the piston pump.
 31. The piston pump according to claim 20, further comprising an outlet valve, the outlet valve having a valve-closure element and a spring element in order to open and close a through opening, the spring element being embodied in the form of a spring ring.
 32. The piston pump according to claim 31, wherein the spring ring has a slit.
 33. The piston pump according to claim 31, wherein the slit splits the spring ring in the width direction and is essentially Z-shaped.
 34. The piston pump according to claim 31, wherein the spring ring is accommodated in a groove in the cylinder element of the piston pump.
 35. The piston pump according to claim 31, wherein the inside of the spring ring is provided with a recess in order to at least partially accommodate the valve-closure element.
 36. The piston pump according to claim 32, wherein the inside of the spring ring is provided with a recess in order to at least partially accommodate the valve-closure element.
 37. The piston pump according to claim 31, further comprising a through opening which the outlet valve is able to open and close, the through opening being situated in the cylinder element of the piston pump in such a way that a movement direction of the piston is perpendicular to an outflow direction through the through opening.
 38. A brake system or stability system for a vehicle, including a piston pump according to claim
 19. 